Impulse axial-flow compressor



Jan. 31, 1961 F. DALLENBACH 2,959,908

IMPULSE AXIAL-FLOW COMPRESSOR Original Filed April 27, 1953 4Sheets-Sheet 1 FREDERICK DALLE/VBA 671$ INVENTOR.

BY fflmMa,

ATTORNEY Jan. 31, 196E F. DALLENBACH IMPULSE AXIAL-FLOW COMPRESSOROriginal Filed April 27. 1953 4 Sheets-Sheet 2 FREDERICK DALLE/VBACH,

INVENTOR.

ATTORNEY Jan. 31, 1961 F. DALLENBACI-I IMPULSE AXIAL-FLOW COMPRESSOR 4Sheets-Sheet 3 Original Filed April 27, 1953 DIRECTION OF ROTATION PLANEOF ROTATION AXIS OF ROTAT FREDERICK DALLE/VBA CH,

INVENTOR.

F w H m m 0 PR ATTORNEY Jan. 31, 19611 F. DALLENBACH 2,969,908

IMPULSE AXIAL-FLOW COMPRESSOR Original Filed April 2'7, 1953 4Sheets-Sheet 4 FREDERICK DALLENBA cw, INVENTOR.

Unite States atent IMPULSE AXIAL-F LOW COMPRESSOR OriginalapplicationApr. 27, 1953, Ser. No. 351,155,

now Patent No. 2,923,461, dated Feb. 2, 1960. Di-

vided and this application Feb. 24, 1958, Ser. No. 717,244

6 Claims. (Cl. 230-117) This invention relates to a compressor and moreparticularly to an impulse axial-flow compressor.

This application is a true division of my application Serial No.351,155, filed April 27, 1953, entitled Impulse Axial-Flow Compressor,now Patent No. 2,923,461, issued February 2, 1960.

An object of this invention is to provide an impulse axial-flowcompressor which is capable of producing a large pressure rise at lowrotational speed.

Another object of this invention is to provide an impulse axial-flowcompressor which is capable of delivering increasing pressure rises withincreasing air flow at constant rotational speed.

Another object of this invention is to provide a novel rotor and statorcombination having high efficiency.

Another object of this invention is to provide an impulse axial-flowcompressor wherein the impulse rotor blades are cooperatively arrangedwith tandem cascade stator blades capable of deflecting the air leavingthe rotor through large turning angles, thereby converting the kineticenergy of the air leaving the rotor into a maximum useful staticpressure rise.

Another object of the invention is to provide a rotor structure andtandem cascade stator blades cooperatively arranged therewith, forpreventing separation of flow on the stator blades, and therebyaccomplishing efficient and relatively high static pressure recovery inthe operation of the impulse axial-flow compressor.

Another object of the invention is to provide an impulse axial-flowcompressor which is particularly desirable for use in connection withsupercharging, cooling and ventilating equipment, when operated at highaltitude, since the present compressor is capable of delivering greaterair weight flow, at low densities, than do conventional compressors.

It is another object of the invention to provide an impulse axial-fiowcompressor which is capable of operating with low power absorption atreduced fiow deliveries and high inlet air densities.

Another object of the invention is to provide an impulse axial-flowcompressor driven by an air-cooled electric motor, wherein the statorand rotor structures thereof are both air-cooled and in which a thermalprotector switch is remote from direct influence of air used to cool themotor, thereby permitting accurate control of the maximum allowablemotor temperature to be maintained.

Another object of the invention is to provide an efficient mechanicalarrangement for adequate cooling of both the rotor and the statorstructures of an electric motor employed for driving the compressor.

Another object of the invention is to provide an efficient and compactimpulse axial-flow compressor driven by an air-cooled thermallyprotected electric motor capable of reliable operation when subject torelatively high temperature motor cooling air and when the compressoris-operating on high temperature air.

Another object of the invention is to provide an impulse axial-flowcompressor driven by an electric motor Patented Jan. 31, 1961 wherein amotor cooling fan is capable of utilizing a separate source of air, suchas ambient air, to cool the motor independently of the source ofcompressor inlet Another object of the invention is to provide anett'ec-' tive sealing means, interposed between the compressor rotor andthe motor cooling fan, which prevents substantial air leakage from thecompressor to the cooling fan.

Still another object of the invention is to provide novell ducting meansforming an integral part of the compressor structure and extending tothe exterior thereof, for discharging the air employed to cool theelectric motor.

A further object of the invention is to provide an impulse axial-flowcompressor having a novel combinedl motor cooling duct and compressordelivery duct arrangement.

Further objects and advantages of the invention will appear from thespecification and the accompanying;

drawings in which:

Figure 1 of the drawing is a longitudinal sectional? view of an impulseaxial-flow compressor in accordancewith the present invention showingparts and portions. in elevation to facilitate the illustration;

Fig. 2 is a transverse half-sectional view taken on the:

line 22 of Fig. 1;

Fig. 3 is a fragmentary inlet end view of the impulse axial-flowcompressor;

Fig. 4 is an enlarged fragmentary sectional view taken.- on line 44 ofFig. 1, showing the impulse compressor rotor blades and the tandemstator blades structure rela-- tive thereto;

Fig. 5 shows the velocity vector diagram of the air' in a direction asshown in Fig. 4 of the drawing. The: rotor blades 9 are airfoilsections, having respective lead ing and trailing edges 9a and 9b. Theseblades 9 are axial-flow compressor blades and may embody a variety ofconfigurations peculiar to certain requirements and! operatingconditions of a compressor constructed according to the presentinvention. As shown in Fig. 6, the slope of the mean camber line 90 atthe trailing edge 9b of each blade is disposed at an angle 7 less than90 to the plane of rotation and the trailing edge 9b is directed towardthe direction of rotation. The preferred angle 7 between the mean camberslope lines 9c of the trailing edges of the rotor blades 9 and the planeof rotation lies between 30 and 50. The shape of the rotor blades 9 issuch that air entering the blades has a velocity imparted thereto, andthe direction of such airflow defines an angle less than 90 to the planeof blade rotation. The air passing through the rotor blades is turnedand the relative velocities of the air therethrough are in the directionof wheel rotation.

The mean camber lines of the stator blades 10 and 11 are designated Aand B respectively. The mean camber line slope at the leading edge 10aof each stator 1 blade 10 is substantially parallel to the direction ofair As shown in Fig. 4, the trailing edges of the stator blades areaxially and tangentially spaced from the leading edges of the statorblades 11, whereby the wake of the trailing surfaces of the statorblades 10 does not flow over the stator blades 11, but passes betweensuccessive ones of the blades 11, thereby avoiding high losses ofefficiency in the second stage stators 11. The mean camber line slope atthe trailing edges 11b of the stator blades 11 is substantially parallelwith the axis of the rotor 8.

As shown in Fig. 4 of the drawing, the air enters the rotor 8 atapproximately axial parallelism therewith, and after discharge from therotor the air is turned by the tandem cascade arrangement of the statorblades Hand 11, whereby it again flows in approximately axialparallelism with the rotor. Due to the aforedescribed characteristics ofthe impulse type of rotor blading, air

leaves the rotor with an increased kinetic energy with substantially nochange of static pressure across the rotor. This kinetic energy of theair leaving the wheel is converted into a static pressure rise in thetandem cascade blade arrangement by turning the air leaving the rotorinto essentially the same direction as that of the air entering therotor. The tandem cascade stator blades 10 and 11 prevent separation offlow, thereby preventing turbulence and maintaining substantiallylaminar fiow, to accomplish efficient and relatively high staticpressure recovery.

Referring particularly to Fig. of the drawings, it will be seen thatspecific relationships of velocities referred to are graphicallyillustrated. C denotes the vectorial measure of the absolute velocity ofthe air entering the rotor blades, while a indicates the angle of theabsolute velocity of the air entering the rotor blades. 11 di otes theperipheral velocity of the rotor blades, while W denotes the relativevelocity of the air entering the rotor. The direction of the relativevelocity of the air entering the rotor is denoted by 6 The absolutevelocity of the air leaving the rotor blades 9 is represented by C whilethe relative velocity of the air leaving the rotor blades 9 isrepresented by W The direction of the absolute velocity of the airleaving the rotor blades 9 is represented by a while the direction ofthe relative velocity of the air leaving the rotor blades 9 isrepresented by 8 The vectorial measure of the absolute velocity of theair entering the stator blades 10, forming the first stage of the tandemstator cascade, is represented by C while the vector of the absolutevelocity of the air, leaving the stator blades 10, forming the firststage of the tandem stator cascade, is represented by C Thus, thevectorial measure of the absolute velocity of the air entering thestators 11, forming the second stage of the tandem stator cascade, issubstantially C while the vectorial measure of the absolute velocity ofthe air leaving the second stage tandem stator cascade is represented byC all as shown in Fig. 5 of the drawing. 04 represents the direction ofthe absolute velocity leaving the first stage of the tandem statorcascade, while 06 represents the direction of the absolute velocityleaving the second stage of the tandem stator cascade With reference toFig. 5 of the drawing, the absolute velocities may be readily comparedwith direct relation: ship to how through various components of thecompressor shown in Fig. 4. A comparison of C with C and C provides aproportional comparison of the absolute velocities during deceleratedflow through the tandem stator cascade.

The rotor 8, together with the blades 9, is driven at a constant speedby the electric motor, which will be hereinafter described in detail.

As shown in Fig. l of the drawing, the impulse axialflow compressor isprovided with a compressor rotor wheel 8 is, supported on. the shaftmember 12 of the.

electric motor rotor 13. The rotor 13 is provided with an enlargedhollow cylindrical shaft member 14 fixed to the flange 15 of the shaft12. The opposite end of the hollow cylindrical shaft member 14 is fixedto the flange 16 of the hollow shaft member 17. The shaft members 12 and17 are supported in bearings 18 and 19 respectively, which maintainconcentric relationship of the rotor wheel 8, the motor rotor 13, andthe impeller 20, relative to the casing structures of the compressor.These bearings 18 and 19 are. retained in opposite ends, 26 and 27, ofthe heat exchanging casing 21. The heat exchanging casing is fixedinternally of the compressor duct casing 22 by means of the bolts 23.The bolts 24. and 25. secure the ends 26 and 27 of the heat exchangecasing to the cylindrical section 28 thereof, as shown best in Fig. 2 ofthe drawings. The cylindrical section 28 of the heat exchanging casing21 is provided with a plurality of radially extending heat exchangingfins 29 which project therefrom and extend into close proximity to theinner wall 30 of the compressor duct casing 22. Supported on the outerside of the hollow cylindrical shaft portion 14 of the rotor 13 are therotor windings 31, and fixed to the inner wall of the cylindrical casingsection 28 of the heat exchanging casing 21 are the motor statorwindings 32. The electric motor of this impulse axial-flow compressor isof the polyphase type having short-circuited rotor windings.

Communicating with the stator windings internally of the heat exchangecasing is the thermal protector switch 33. The switch embodies aconventional arrangement, including a thermally responsive element. Thethermal protector switch is supported in the casing end member. 27 ofthe heat exchange casing and is arranged to interrupt the fiow ofcurrent to the electric motor in the event it is overheated to apredetermined degree. The heat exchanging casing portion 28, togetherwith the inner wall 30 of the compressor duct casing 22, provides a ductsurrounding the heat exchanging fins 29. This duct, outwardly of theheat exchanging casing 21, provides a passage for air, which cools themotor without affecting the operation of the thermal protector switch,while the latter senses the temperature of the stator windings. The ductdefined by the casing walls 28 and 30 communicates with the outlet 34 ofthe impeller 20. This impeller is carried by the shaft 12 and isprovided with an inlet 35 communicating with ambient air, flowing asindicated by the arrow 36. Positioned between the inner and outer walls40 and 41, respectively, of the compressor duct casing 22 are thecompressor stator blades 10 and 11. The blades 10 are provided with airpassages 39, which extend radially therethrough, providing a passage forthe air as indicated by arrow 36, permitting direct communication withthe inlet 35 of the impeller 20. Communicating with the outlet 34 of theimpeller 20 are openings 12a which serve as passages to conduct air intothe bore portion 12b of the shaft 12. Seal structures 38 and 38a provideconfining walls for the entrance of air passing to the inlet 35 of theimpeller 20. The seal 38a is arranged to prevent leakage of air from thecompressor wheel 8 to the inlet of the impeller 20. The upstream sectionof the compressor duct casing 22 is connected to the downstream sectionthereof by means of the bolts 42. The inner and outer walls 40 and 41,respectively, align with the inner and outer walls 30 and 37,respectively, forming a continuous annular duct for air flowing in adirection as indicated by the arrow 43. The compressor duct casing 22near the downstream end thereof is provided with radially extendingpassages 44. These passages communicate with the duct inwardly of thecasing wall 30 and with the fins 29 of the heat exchanging casing 21.The compressor duct 22 is provided with outlet openings 45, which aredisposed intermediate the passages 44, as shown in Fig. 2 of thedrawing. The

outlet openings v 45. communicate with the interior of a duct 46, whichis connected to a flange 47 of the compressor duct casing 22.

The operation of the impulse axial-flow compressor is substantially asfollows: When the electric motor is energized, the rotor 13 thereofrevolves in the bearings 18 and 19, thereby rotating the rotor wheel 8,causing the blades 9 thereof to impel air toward and past the statorblades 10 and 11 and through the compressor duct casing 22, as indicatedby the flow line in Fig. 4 of the drawings. The air passes into the duct46, which conducts it to the desired point.

Under certain operating conditions, the flow of air through thecompressor duct 22 is at fairly high temperature; therefore, it isnecessary to provide very efiicient means for cooling the electric motorinternally of this compressor duct. The passages 39 extending throughthe stator blades 10 provide airinlets communicating with the impelleroutlet 34. The air flow through the passages 39, as indicated by thearrows 36, at times may be heated, but is preferably cool ambient airfor cooling the motor. The air entering the impeller 20 is relativelydense as compared with the air which has dissipated heat from the motor.This air is acted upon by the impeller 20 before the air is heated bythe motor, in order to maintain efiicient operation of the impeller. Theimpeller is centrifugal in operation and its peripheral outletcommunicates with the heat exchanging fins 29 projecting from the heatexchanging casing 21. The hollow cylindrical portion 28 of the heatexchanging casing 21 is arranged in thermally conductive relationshipwith the motor stator windings 32, in order to exchange heat from themotor without introducing cooling air into the area of the statorwindings. The thermal protector switch 33 communicates with the interiorof the heat exchanging casing 21 and senses the temperature of thestator windings for the purpose of shutting off the supply ofelectricity to the motor in the event it becomes overheated. Air whichpasses in heat exchange relationship with the fins 29 is exhaustedthrough the radially extending passages 44, together with the air forcedthrough the hollow rotor structure of the electric motor, as indicatedby the arrows 17a. The thermal protector switch 33, having itstemperature sensing element internally of the heat exchanging casing 21,is, therefore, capable of responding to a predetermined temperature risein the stator winding without any direct thermal mfluence of the coolingair which absorbs heat from the stator and rotor structures of themotor. The cooling air passing internally on the inner wall 30 of thecompressor duct 22 also prevents heat exchange from the compressor duct22 to the electric motor.

I claim:

1. An axial-flow compressor comprising: an electric motor having arotor; motor field windings spaced from said rotor and surrounding thesame; a heat exchanging casing surrounding said windings; a secondcasing spaced from said heat exchanging casing and forming a ducttherewith for directing air in heat exchanging relationship with saidheat exchanging casing; a cooling air impeller operatively associatedwith and driven by said rotor, causing air to flow through said duct; athird casing surrounding said second-mentioned casing and forming asecond duct outwardly thereof; a compressor wheel spaced axially fromsaid cooling air impeller, said compressor wheel being connected to saidrotor and having blades adapted to force air through saidsecond-mentioned duct; and seal means intermediate said compressor wheeland said impeller to prevent leakage of air from said wheel to saidimpeller.

2. An axial-flow compressor comprising: an electric motor having arotor; motor field windings spaced from said rotor and surrounding thesame; a heat exchanging casing surrounding said windings; a secondcasing spaced from said heat exchanging casing and forming a ducttherewith for directing air in heat exchanging relationship with saidheat exchanging casing; a cooling air impeller operatively associatedwith and driven by said rotor, causing air to flow through said duct; athird casing surrounding said second-mentioned casing and forming asecond duct outwardly thereof; a compressor wheel connected to said.rotor and having blades adapted to force air through saidsecond-mentioned duct; and compressor stator vanes in saidsecond-mentioned duct arranged to cooperate with said compressor wheel,said stator vanes having openings extending therethrough to the exteriorof said third casing and forming air passages communicating with saidimpeller.

3. An axial-flow compressor comprising: an electric motor having arotor; motor field windings spaced from said rotor and surrounding thesame; a heat exchanging casing surrounding said windings; a secondcasing spaced from said heat exchanging casing and forming a ducttherewith for directing air in heat exchanging relationship with saidheat exchanging casing; a cooling air impeller operatively associatedwith and driven by said rotor, causing air to flow through said duct; athird casing surrounding said second-mentioned casing and forming asecond duct outwardly thereof; a compressor wheel spaced axially of andconnected to said impeller, said wheel having blades adapted to forceair through said second-mentioned duct; compressor stator vanes in saidsecond-mentioned duct arranged to cooperate with said compressor wheel,said stator vanes having openings extending therethrough to the exteriorof said third casing and forming passages for air communicating withsaid impeller; and a seal intermediate said compressor wheel and saidimpeller, arranged to prevent leakage of air from said wheel to saidimpeller.

4. An axial-flow compressor comprising: casing means forming anelongated chamber with end walls, said chamber being surrounded by aworking air passage with inlet and outlet ends; an electric motorsupported within said chamber and spaced from the side and end walls toprovide a cooling air passage, said motor having a rotor with a coolingair passage extending therethrough and communicating with the spaces atthe ends of said chamher, said spaces communicating with the ambientatmosphere; heat dissipating means between said motor and the side wallof said chamber; a cooling air impeller connected with said rotor in thespace at one end of said chamber, said impeller causing air flow aroundsaid motor and through said rotor; and a compressor wheel secured tosaid rotor beyond one of the chamber end walls, said wheel having bladesprojecting into the working air passage adjacent the inlet end andserving to force air through said passage.

5. An axial-flow compressor comprising: casing means forming anelongated chamber with end walls, said chamber being surrounded by aworking air passage with inlet and outlet ends; an electric motorsupported within said chamber and spaced from the side and end walls toprovide a cooling air passage, said motor having a rotor with a coolingair passage extending therethrough and communicating with the spaces atthe ends of the chamber, said spaces communicating with the ambientatmosphere; heat dissipating means between said motor and the side wallof said chamber; partition means dividing the space at one end of saidchamber into intake and outlet sections; a centrifugal air impellerconnected with said rotor in the outlet section of said end space, theintake of said impeller communicating with said intake section, saidimpeller causing air flow around said motor and through said rotor; anda compressor wheel secured to said rotor beyond one of the chamber endwalls, said wheel having blades projecting into the working air spaceadjacent the inlet end and serving to force air through said passage.

6. An axial-flow compressor comprising: casing means forming anelongated chamber with end walls, said chamber being surrounded by aworking air passage with inlet 7 and outlet ends; an electric motorsupported within said chamber and spaced from the side and end walls toprovide a cooling air passage, said motor having a hollow rotor withcooling air passages communicating with the spaces at the ends of thechamber, said spaces communicating with the ambient atmosphere; radiallyextending heat dissipating vane means between said motor and the sidewall of said chamber; partition means dividing the space at one end ofsaid chamber into intake and outlet sections; a centrifugal air impellerconnected with said rotor in the outlet section of said end space, theintake of said impeller communicating with said intake section, saidimpeller causing air flow around said motor and through said rotor; acompressor wheel secured to said rotor beyond one of the chamber endwalls, said wheel having blades projecting into the working air spaceadjacent the inlet end and serving to force air through said p ssa d.ifi sins ne n d working a e at the downstream side of said wheel blades,certain of saidvanes being hollow to provide cooling air flow to theintake section ofthev Space at one end of said chamber.

References Cited in the file of this patent UNITED STATES PATENTS

